Food products containing partially and/or totally denatured milk proteins

ABSTRACT

The present invention relates to a dietary composition produced by a process involving extruding a milk containing product (e.g., milk, milk concentrate, milk protein concentrate, whey, whey concentrate, whey protein isolate, whey protein concentrate) through an extruder at about 50-about 450 rpm and at a temperature of about 40° to about 120° C. to produce the dietary fiber composition (which contains partially or totally denatured milk containing product). The present invention also concerns a food product containing at least one food ingredient and the dietary composition described herein; for example the dietary composition containing partially denatured proteins may be used to create a fully cooked, totally expanded or puffed ready-to-eat snack food product (or pellets or half products). In addition, the present invention relates to a method of making a food product, involving adding the dietary composition described herein to one or more food ingredients or adding one or more food ingredients to the dietary composition described herein. Furthermore, the present invention concerns a method of increasing fiber in the diet of a mammal, involving feeding to the mammal the fiber enriched food product described herein.

REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. patent application Ser. No.10/686,834, filed 16 Oct. 2003, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a dietary composition produced by aprocess involving extruding a protein containing product (e.g., milkprotein containing product such as milk, milk concentrate, milk proteinconcentrate, whey, whey concentrate, whey protein isolate, whey proteinconcentrate) through an extruder at about 50-about 450 rpm and at atemperature of about 40° to about 120° C. to produce the dietarycomposition (which contains partially or totally denatured milk proteincontaining product). The present invention also concerns a food productcontaining at least one food ingredient and the dietary fibercomposition described herein. In addition, the present invention relatesto a method of making a food product, involving adding the dietary fibercomposition described herein to one or more food ingredients or addingone or more food ingredients to the dietary fiber composition describedherein. Furthermore, the present invention concerns a method ofincreasing fiber in the diet of a mammal, involving feeding to themammal the fiber enriched food product described herein.

As the reports of the health and nutraceutical benefits of consumingdietary fibers continue to grow, research is focused on increasing theamount, content and quality of fibers in human diet. Consumers as wellas nutrition-focused professional organizations are demanding increasedamounts of fiber in processed foods. The results of recent surveys ofthe amount of fiber consumed by Americans reveal that most consume lessthan 50% of the estimated desirable daily fiber intake. Current averagefiber intake is estimated at about 12 g/day, but the American DieteticAssociation recommends 20-35 g/day (J. Am. Dietetic Assoc., 93:1446-1447 (1993)).

Foods rich in fiber help with the management of a host of conditions.Associated healthful benefits of increasing fiber consumption includereduced risk of some types of cancer (including breast cancer) andcoronary heart disease, regulation of blood glucose and insulin,lowering the concentration of blood lipids, reduced risk ofcardiovascular disease and controlling diabetes, alleviatingconstipation, hemorrhoids and diverticulitis (Wolk, A., et al., JAMA,281(21): 1998-2004 (1999); Kritchevsky, D., Cereal Foods World, 42(2):81-85 (1977)). Thus it is desirable and beneficial to increase theamount of fiber in most prepared foods.

The Food and Agricultural Organization/World Health Organization(FAO/WHO), 1995 Codex Alimentarius Commission defines dietary fiber as,“the edible plant or animal material not hydrolyzed by the endogenousenzymes of the human digestive tract as determined by the agreed uponmethod.” Typical fiber sources are plant-based and include grains,fruits and vegetables; other less-traditional food fibers includeChitosan, a fat-binding dietary fiber derived from shellfish, andpolymeric components such as cell-wall proteins and phenolic compoundssuch as tannin and cutin.

Traditionally, the food industry uses native (folded) whey proteins fortheir functional and nutritional properties in formulating differentfoods. Though new products incorporating whey proteins, such as sportsdrinks, are being developed, innovation in process and productdevelopment is still needed (Anon., American Dairy Products Institute,Bulletin No. 25, p. 17 (2000)). Fortifying snacks with whey proteinscould provide a particularly attractive outlet for surplus wheyproteins; however, this practice has been limited due to known adversetextural effects when the whey protein concentrate supplementation isgreater than 10% of the main starch component (Kim, C. H., and J. A.Maga, Lebensmittel-Wissenchaft und-Technologie, 20: 311-318 (1987)).

The present invention provides, in one aspect, proteins (e.g., wheyproteins) that are totally denatured and are insoluble to enzymes andprotein cleaving chemicals (e.g., urea). The new product is indigestibleand can therefore serve as a fiber source. The fiber-like productdescribed in this invention may be from an animal source (e.g., milk),but its properties are physiologically similar to plant-source dietaryfiber, thus serving as a bulking agent and being nondigestible toenzymes. Alternate use for this product include use in biodegradableproducts and utilization in ingredients that require low gellingtemperatures.

SUMMARY OF THE INVENTION

The present invention relates to a dietary composition produced by aprocess involving extruding a milk protein containing product (e.g.,milk, milk concentrate, milk protein concentrate, whey, wheyconcentrate, whey protein isolate, whey protein concentrate) through anextruder at about 50-about 450 rpm and at a temperature of about 40° toabout 120° C. to produce the dietary composition (which containspartially or totally denatured milk protein containing product). Thepresent invention also concerns a food product containing at least onefood ingredient and the dietary composition described herein. Inaddition, the present invention relates to a method of making a foodproduct, involving adding the dietary composition described herein toone or more food ingredients or adding one or more food ingredients tothe dietary composition described herein. Furthermore, the presentinvention concerns a method of increasing fiber in the diet of a mammal,involving feeding to the mammal the fiber enriched food productdescribed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows electron micrograms of whey protein isolates (WPI): (A)scanning microscopy was used to examine dry powder; (B) the non extrudedWPI Paste (40% moisture) was embedded, stained with uranyl acetate andsections examined by transmission electron microscopy; (C) extruded(100° C.) WPI (40% moisture) treated as in (B);

FIG. 2 shows SDS PAGE of extruded whey isolates: (A) with2-mercaptoethanol; (B) without 2-mercaptoethanol; the lanes are: 1=100°C.; 2=75° C.; 3=50° C.; 4=35° C.; 5=Native WPI; 6=laboratory whey;

FIG. 3 shows transmission electron micrographs of whey protein isolates(WPI) positively stained with uranyl acetate and lead citrate: (A)enlargement of denatured whey as in FIG. 1C; (B) enlargement of aselected protein-dense area of FIG. 1B; (C) Fast Fourier Transforms ofelectron density images of native WPI; and (D) Fast Fourier Transformsof electron density images of denatured WPI; and

FIG. 4 shows electron-density mapping corresponding to the FourierTransforms (A) for denatured and native WPI, and (B) inverse reciprocalspacing of electron-density images.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a dietary composition containingpartially or completely denatured proteins. The dietary composition isproduced by a process wherein the proteins in a protein containingproduct (e.g., milk protein containing product such as milk, milkconcentrate, milk protein concentrate, whey, whey concentrate,preferably whey protein isolate) are partially or completely denatured.This process involves processing the protein containing product throughan extruder (e.g., single screw extruder, preferably twin screwextruder) at low shear (generally about 50-about 450 rpm (e.g., 50-450rpm), preferably about 50-about 300 rpm (e.g., 50-300 rpm), morepreferably about 50-about 200 rpm (e.g., 50-200 rpm), most preferablyabout 50-about 100 rpm (e.g., 50-100 rpm)), at a temperature in theextruder of about 40′ to about 120° C. (e.g., 40′ to 120° C.). Pressuresmay range from about 10 to about 2000 psi (e.g., 10-2000 psi, preferablyabout 500 to about 1500 psi (e.g., 500-1500 psi), more preferably about800 to about 1200 psi (e.g., 800-1200 psi)), and torque may range fromabout 30 to about 70% (e.g., 30-70%, preferably about 45 to about 55%(e.g., 45-55%)). Residence time of the protein containing product in theextruder is generally about 15-about 90 seconds (e.g., 15-90 seconds),preferably about 20-about 75 seconds (e.g., 20-75 seconds), and morepreferably about 35-about 60 seconds (e.g., 35-60 seconds). To produce adietary composition containing completely denatured proteins, thetemperature generally is about 90° to about 120° C. (e.g., 90° to 120°C.), more preferably about 950 to about 120° C. (e.g., 95° to 120° C.),most preferably about 100° to about 110° C. (e.g., 1000 to 110° C.); theshear is preferably about 50 to about 100 rpm (e.g., 50-100 rpm).Completely denatured proteins are generally ≧95% (e.g., 95%) denatured,preferably ≧99% (e.g., 99%) denatured, more preferably about 100% (e.g.,100%) denatured. To produce a dietary composition containing partiallydenatured proteins, the temperature generally is about 40° to about 90°C. (e.g., 40° to 90° C.), more preferably about 55° to about 80° C.(e.g., 550 to 80° C.), most preferably about 60° to about 70° C. (e.g.,60° to 70° C.); the shear is preferably about 150 to about 250 rpm(e.g., 150-250 rpm). Partially denatured proteins are generally <95%denatured, preferably <about 90% (e.g., <90%) denatured, more preferablyabout 40-about 80% (e.g., 40-80%) denatured. Low shear increases theresidence time of the milk containing product in the extruder sinceresidence time is a function of the rpm of the extruder, the residencetime can increase from 45 to 90 seconds. The process may also utilizeother proteins such as, for example, soy protein, vegetable protein,animal protein. The dietary composition is a dietary fiber compositionwhen it contains completely denatured proteins since completelydenatured proteins are indigestible.

The present invention also concerns a food product containing at leastone food ingredient and the dietary composition (containing partially orcompletely denatured proteins or combinations thereof) described above;the food product is a fiber enriched food product if it contains atleast one food ingredient and the dietary composition containingcompletely denatured proteins. The food ingredient may be any foodingredient. For example, the food ingredient may be the ingredients forcookies or muffins such as flour. Furthermore, the food ingredient maybe shelf-stable packaged pre-mixes for preparing food and beveragecompositions, usually requiring the addition of other ingredients (e.g.,eggs, shortening, water or milk) to be supplied and added by thepreparer. Additionally, the food ingredient may be a ready-to-cook mix(combined food ingredients that require additional cooking (e.g.,baking, frying, micro waving) to form a ready-to-eat food or beverageproduct). Generally, the food product (e.g., fiber enriched) may be anyfood product such as a drink, yogurt, or pizza, or a bakery product suchas cake, biscuit, pie crust, cookie, muffin, bread, cereal, doughnut,noodle, brownie, cracker or snack food. The amount of the dietarycomposition contained in the enriched food product may be any amountthat does not adversely affect the food product (for example, the foodproduct may contain about 1% to about 40% of the dietary composition,preferably about 5% to about 30%, more preferably about 5% to about 20%,most preferably about 10% to about 15%).

The dietary composition containing partially denatured proteins of thepresent invention may be used to create a totally expanded or puffedsnack food product (or pellets or half products), which may be fullycooked or ready-to-eat, that also contains at least one food ingredient(e.g., any starch source such as corn, wheat, rice, barley, rye,potato). Currently, unmodified milk protein containing products (e.g.,whey) when added to expanded products collapse the matrix and do notpuff, and thus it is necessary to limit substituting whey for starch toabout 5%. Surprisingly, the dietary composition containing partiallydenatured proteins can replace well over 5% of the starch withoutaffecting puff characteristics while allowing one to obtain desirablecrunch and crispness notwithstanding the high level of milk proteincontaining products contained therein. The dietary compositioncontaining partially denatured proteins can replace more than about 35%of the starch without affecting puff characteristics. Generally, thecomposition containing partially denatured proteins can replace >0% toabout 60% of the starch (e.g., >0-60%), preferably >5% to about 60%(e.g., >5-60%), more preferably about 10-about 50% (e.g., 10-50%), mostpreferably about 20-about 40% (e.g., 20-40%). The totally expanded orpuffed snack food product may contain about 5-about 80% (e.g., 5-80%) ofthe dietary composition containing partially denatured proteins,preferably about 15-about 60% (e.g., 15-60%), more preferably about20-about 40% (e.g., 20-40%). The expanded or puffed food product (orpellets or half products) may be made by methods known in the art. Forexample, the dietary composition containing partially denatured proteinsof the present invention was blended with corn meal at the ratio of 25 gof the dietary composition containing partially denatured proteins and75 g corn meal. The blend of corn meal and the dietary compositioncontaining partially denatured proteins was extruded in a ZSK30 twinscrew extruder (Krupp, Werner & Pfleiderer Company, Ramsey, N.J.)consisting of nine heating-barrel sections each individually controlled;the first six zones were preset at 35°, 35°, 50°, 50°, 75°, and 90° C.respectively, and the last 3 barrel temperatures were set at 100°, 110°and 125° C., respectively. The die plate was fitted with two circularinserts (3.18 mm diameter). Melt temperatures was recorded at the die.The blend was fed into the extruder with a series 6300 digital type 35twin screw volumetric feeder (K-Tron Corp., Pitman, N.J.) at a constantsetting of 800 rpm yielding a feed rate of 128.5 g/min. Water was addedat a rate of 1.3 L/h with an electromagnetic dosing pump (Milton Roy,Acton Mass.) to bring the moisture content of the feed to approximately18 g H₂O/100 g product (wet basis). The screw speed of the extruder wasmaintained at 300 rpm. The screw elements were selected to provide highshear at 300 rpm by adding kneading blocks to the configuration. Theprocess may also utilize other proteins such as, for example, soyprotein, vegetable protein, animal protein, and other carbohydratesources such as wheat, barley, rice, and starch.

The dietary composition containing completely denatured proteins of thepresent invention can be added to baked sweet wafers to offer anothertype of protein enrichment to cookies or snack bars. It may also bepossible to utilize the dietary composition containing completelydenatured proteins of the present invention in meal extenders and meatalternatives, function as instant thickeners for beverage and dairyapplications, and also finding use as edible films and encapsulatingagents. The dietary composition containing completely denatured proteinsof the present invention may also function as an instant thickeningproduct which can be used in place of starch and other hydrocolloids;potential applications include baby food, sports drink and dairy foodssuch as sour cream, yogurt and cottage cheese.

The possibilities for the dietary composition containing completelydenatured proteins of the present invention extend past the groceryaisle. The dietary composition containing completely denatured proteinsof the present invention may make oxygen, aroma and oil barrier films atlow-to-intermediate relative humidity; may provide mechanical propertiesand adequate functionality when used as coating or encapsulating agents,providing durability when applied directly on foods or as films whenseparating layers of heterogeneous foods, or films formed into pouchesfor food ingredients; and may also be used as encapsulating agents.

Additionally, the present invention also relates to a method of making afood product involving adding the dietary composition of the presentinvention to one or more food ingredients (or vice versa). For example,in making cookies or muffins, the dietary composition of the presentinvention can partially substitute for flour or be added in addition toflour in the preparation of cookies or muffins. If cooking (e.g.,baking, frying, micro waving) is required, then normal cookingconditions are utilized.

Furthermore, the present invention concerns a method of increasing fiberin the diet of a mammal involving feeding to the mammal the fiberenriched food product described herein. Generally, the mammal is ahuman.

Denaturation of proteins such as milk containing products may bemeasured by methods known in the art, including the solubility index andthe method of Kilara (Kilara, A., J. Dairy Sci., 67:2734-2744 (1984))where protein insolubility (denaturation) was calculated as: (% TotalProtein−% Soluble Protein=% Insoluble (denatured)). Proteins which arepartially denatured will absorb more water than proteins which aretotally denatured. Partially denatured proteins are partly soluble andpartly insoluble depending on the temperature and severity of shear.Totally denatured proteins are totally insoluble.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which the invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are now described.

The following examples are intended only to further illustrate theinvention and are not intended to limit the scope of the invention asdefined by the claims.

EXAMPLES

Materials And Methods:

Whey protein concentrate (ALACEN 834) and lactalbumin (ALATAL 825) werepurchased from New Zealand Milk Products, Inc. (Santa Rosa, Calif.).Whey Protein Isolate (PROVON 190) was purchased from GlanbiaIngredients. The compositions were as follows: WPC80 (whey proteinconcentrate, 80% protein), moisture 2.8%, protein 83.6%, fat 0.8, ash3.3%, carbohydrate by difference; WLAC (whey lactalbumin), moisture5.5%, protein 89.9%, fat 3.8, ash 0.5%, carbohydrate by difference; WheyProtein Isolate (WPI), moisture 2.8%, protein 89.6%, fat 25, ash 3.3%,carbohydrate by difference.

A ZSK-30 twin screw extruder (Krupp Werner Pfleiderer Co., Ramsey, N.J.)with a smooth barrel was used. The extruder had nine zones, and theeffective cooking zones 6, 7, 8, and 9 were set to the same temperaturefor each test. To achieve different melt temperatures the cooking zoneswere set to the same barrel temperature of 35, 50, 75, or 100° C.respectively. Zones 1 to 3 were set to 35° C. and zones 4 and 5 were setto 75° C. Melt temperature was monitored behind the die. The die platewas fitted with two circular inserts of 3.18 mm diameter each. The screwelements were selected to provide low shear at 300 rpm; the screwprofile was described by Onwulata et al. (Onwulata, C. I., et al., J.Food Sci. Vol., 63(5): 814-818). Feed was conveyed into the extruderwith a series 6300 digital feeder, type T-35 twin screw volumetricfeeder (K-tron Corp., Pitman, N.J.). The feed screw speed was set at 600rpm, corresponding to a rate of 3.50 kg/h. Water was added into theextruder at the rate of 1.0 L/h with an electromagnetic dosing pump(Milton Roy, Acton, Mass.). Samples were collected after 25 min ofprocessing, freeze-dried overnight in a VirTis Freeze Mobile 12XLResearch Scale Freeze Dryer (Gardiner, N.Y.), and stored at 4.4° C.until analyzed. The experiments were performed in triplicate.

Analysis of variance was used to identify differences in physicalproperties at various processing conditions. Duncan's multiple rangetest was used for mean separation and correlation coefficients werecalculated. The Statistical Analysis System (SAS) package was used (SASInstitute Inc, Cary, N.C.) in all cases. Significance of differences wasdefined as P≦0.05.

Moisture was determined by the AOAC (Association of Official AnalyticalChemists) Official Method 925.10. Extrudate samples weighingapproximately 1.5 g were dried in a vacuum oven at 100° C. overnight(AOAC, 2000, Official Methods of Analysis, 14th ed., Association ofOfficial Analytical Chemists, Washington, D.C.).

Ash was determined by the AOAC Official Method 923.03. Ash wasdetermined for each sample using 3 g assayed in a Muffler furnace at550° C. for 16 h; percent ash was calculated.

Fat was determined using the AOAC Official Method 30-25. One gramextrudate sample was placed in an Erlenmeyer flask and 1 ml of sulfuricacid and 4 ml water was added to the flask. The samples were mixedgently and after 60 min were transferred to a 60 ml separatory funnelusing 25 ml of dichloromethane: methanol solution (1:1). Extrudatesamples were shaken and allowed to separate for 15 min. The bottom layerwas drained into a weighing pan and then evaporated, and the amount offat determined (American Association of Cereal Chemists, 1995, ApprovedMethods of the American Association of Cereal Chemists, 9th Edition.,The Association, St Paul, Minn.).

Protein was determined with 0.2 g extrudate analyzed with the LECOProtein Analyzer Model FP2000 (LECO Corporation, St. Joseph, Mich.).Percent protein was calculated with the nitrogen conversion factor 6.38for whey protein.

Gel strength was measured by Bloom determinations with a TA-XT2 TextureAnalyzer (Ju, Z. Y., and A. Kilara, J. Food Sci. 63(2):288-292 (1998)).A 12% WPI solution was made (3.204 g of ground freeze-dried sample mixedwith 26.7 ml deionized water and 3.3 ml 0.03 M CaCl₂), and allowed tosit for 15 min in a 50×70 mm cylindrical jar. The sample was heated to80° C. for 30 min in a water bath, cooled in an ice bath for 15 min andthen stored overnight at 4° C. The specimen was thawed at 25° C. in 50%relative humidity room. Gel strength was determined with a TA-XT2Texture Analyzer running a penetration test with a 30 mm analyticalprobe to a depth of 6 mm at the rate of 1 mm/sec. The weak gels wereeasily deformed with evidence of syneresis.

Protein insolubility was determined with 1.0 g ground freeze-driedextrudate sample mixed with 90 ml deionized water. The proteinsuspension was stirred at 125 rpm at pH 7.0 for 2 h. The suspension wascentrifuged for 20 min and the supernatant was freeze dried overnight.The LECO Protein Analyzer Model FP2000 (LECO Corporation, St. Joseph,Mich.) was used to analyze the solids from the supernatant for proteincontent. Protein insolubility (denaturation) was calculated (Kilara, A.,J. Dairy Sci., 67:2734-2744 (1984)) as: (% Total Protein−% SolubleProtein=% Insoluble (denatured)).

Foam volume and stability of extruded proteins were determined byheating 2.3 g samples mixed with 35 ml deionized water to 60° C. for 15min. The slurry was then whipped for 15 sec in Waring Lab MicronizerFPC70 (Waring Products Division, New Hartford, Conn.), then transferredto a 100 ml graduated cylinder where the foam volume was read initially,and then every 5 min for 1 h. Foam stability (foam capacity at specifictime) over the one hour period was calculated.

Protein Digestibility was determined with 10 ml extrudate sampledissolved in distilled water, the pH was adjusted to 8.0 with 0.1 N NaOHor HCl. One milliliter of freshly prepared enzyme stock solution (1.6mg/ml trypsin, 3.1 mg/ml chymotrypsin, and 1.3 mg/ml aminopeptidase) wasadded to the protein suspension at 37° C. The pH after 10 min wasrecorded with a portable pH meter (IQ Scientific Instruments, Inc. SanDiego, Calif.), and a Tris/HCl buffer containing 2.0% SDS (w/v) and 0.1%mercaptoethanol (v/v) was added to the protein solution which wasimmediately heated to 90° C. to terminate the enzymatic reaction.Samples were then analyzed by quantitative gel electrophoresis. The %protein digestibility was calculated by the following equation (Ju, Z.Y., and A. Kilara, J. Food Sci. 63(2):288-292 (1998)): %Digestibility=210.46 B 18.10(X); where X is the pH.

For SDS PAGE assay, samples were vortexed and dissolved in 20 mMTRIS/HCl, 5 mM EDTA, 2.5% SDS with and without 5.0% 2-mercaptoethanol atpH=8.0 then heated in boiling water for 2 min. Bromophenol blue is addedto about 0.1% concentration. The samples were at 2 mg/ml concentration.Phast gels (Amersham Pharmaica Biotech, Uppsala, Sweden) were runaccording to the procedures given by the manufacturer for SDS 20%homogeneous gels. The 6 lane (4 ul per lane) sample applicators wereused. Protein staining used the coomassie blue procedure given by themanufacturer (Farrell, H., E. D., et al., J. Dairy Sci., 81:2974-2984(1998)).

For fine structure, transmission electron microscopy (TEM) was done ofthin sections made from epoxyembedded samples. Millimeter-sized piecesof coarsely ground, freeze-dried segments of ribbons of the extrudateswere immersed in 2.5% glutaraldehyde in 0.1 M imidazole buffer solution(pH 6.8) and stored in sealed vials at 4° C. For embedding and thinsectioning, the segments were washed in imidazole buffer, immersed in 2%osmium tetroxide in 0.1M imidazole buffer for 2 h at room temperature,washed in distilled water, and gradually dehydrated in a series ofethanol solutions and propylene oxide for one hour. Samples were theninfiltrated with a 1:1 mixture of propylene oxide and epoxy resinmixture overnight and finally embedded in epoxy resin. Thin sectionswere cut and stained with 2% uranyl acetate, and lead citrate solutions.TEM was done in the bright field mode using a model CM12 electronmicroscope (FEI/Philips, Hillsboro, Oreg.). Average spacings of electrondensity, corresponding to fine structure in the extrudates, wereestimated from the intensity distribution in Fourier transforms,computed from digital images made from TEM photographic negatives,recorded at 45,000×. Negatives were digitized using a SprintScan 45 filmscanner (Polaroid Corp., Cambridge, Mass.) and square areas of 2.8megabyte images (512×512 pixels) were transformed after flattening,adjustment of brightness and contrast and one cycle of a low pass filterusing a 3H 3 pixel kernel in Image Pro Plus software (Media Cybernetics,Silver Spring, Md.). Line profiles of the radial distribution ofintensity in the Fourier transforms were made, and reciprocal spacingswere calculated based on the location of orders of peaks in transformsof a line grating with an equivalent spacing of 22 nm.

For scanning electron microscopy (SEM), a layer of dry powder particleswas adsorbed onto conductive carbon adhesive tabs glued to aluminumspecimen stubs (Electron Microscopy Sciences, Ft. Washington, Pa.), andthe surface was coated with a thin layer of gold in a model Scancoat Sixsputter coater (BOC Edwards, Wilmington, Mass.). Images of the powderparticles were made with a model JSM 840A scanning electron microscope(JEOL USA, Peabody, Mass.) operating in the secondary electron imagingmode and integrated with a digital image workstation, model Imix1(Princeton Gamma-Tech, Princeton, N.J.).

Results And Discussion:

Extruding whey proteins at the preset temperature of 75° C. resulted invarying degrees of melt temperatures and denaturation for the differentproducts (Table 1; % is percent of denatured proteins). Followingextrusion, whey protein concentrate (WPC80) was the least denatured, andwhey lactalbumin (WLAC) and whey protein isolates (WPI) weresignificantly (p<0.05) more denatured. WPI demonstrated the greatesteffect, changing from 28 to 94.8% denatured. Therefore, furtherexperiments were conducted with WPI.

The effect of extrusion cooking on denatured proteins was examined byelectron microscopy. Changes in the microstructure of WPI and theultrastructure of the denatured proteins are presented in FIG. 1. Themicrostructure of the dry powders, examined by scanning electronmicroscopy, reveal particles ranging from 10 to 50 micrometers indiameter (A). Transmission electron microscopy (B) shows the release ofprotein at the edge of powder particles after brief exposure to watertypical of initial mixing in the extruder; irregular strings andgranules, corresponding to molecular aggregates, ranging from less than10 nm to over 200 nm can be seen (B). In contrast, the ultrastructure ofextruder-denatured insoluble whey protein shows a closely-packedarrangement of electron dense particles, typical of denatured proteinmatrix, ranging from approximately 2 to 6 nm in diameter (C).

With the addition of shear in the extruder, significant unfolding(denaturation) occurred at 75° C. WPI extruded at preset temperatures ator above 50° C. denatured significantly (p<0.05) with increased presettemperature. The pH of the suspended protein remained stable asextrusion temperature increased, but measurable nitrogen (protein)increased as shown in Table 2. Loss of protein nitrogen might beexpected as temperatures increased above 80° C., but we surprisinglyobserved no significant change in protein nitrogen content after drying.Though the amount of protein denatured increased, with increasingtemperature, denaturation had minimal overall effect on proteindigestibility. So the surprising result is increased proteindenaturation without a significant loss of digestibility due toextrusion below 90° C.

The WPI and variously heat treated samples were compared by SDS-PAGE(FIG. 2). SDS gel of the variously denatured WPI indicated minimalchange in solubility (FIG. 2). SDS gels were initially developed withoutreducing reagent so the protein disulfide bonds are intact. Theunreduced samples at 35° C. and 50° C. show somewhat diminished bandsfor the higher molecular weight whey proteins (B). However, at 50° C.and 70° C. samples were equivalent weight, and fainter than the nativewhey or whey proteins produced in the lab on the SDS gel (compare lanes1 and 2 with 6 in FIG. 2). In this respect, the SDS gels parallel thesolubility data in that increased temperature decreases solubility inSDS alone, indicating sulfhydryl-disulfide crosslinking. When thesamples were reduced thoroughly and all disulfide bonds cleaved, all theextruded whey samples at the different temperatures were similar to eachother and to the initial WPI (A). Thus, extruding whey even at thehighest temperatures surprisingly does not affect the overall proteinratios. The native and extruded whey still have the same amount of thedifferent proteins (FIG. 2) and their total nitrogen values were similar(Table 2).

Physical functional properties of extruded WPI such as gel strength,foam volume and stability were significantly affected at and above 75°C., and proportionally at lower preset temperatures. Greater than 30%moisture was needed to extrude the whey protein isolates, but the onlysignificant change in moisture of the extruded products occurred at 100°C. (Table 3). Partial denaturation at temperatures between 35° and 50°C. significantly increased gel strength, but at 75° C. or highercomplete loss of gelling property resulted. Foam volume remained high upto 50° C., but decreased significantly (p<0.05) after 75° C. Foamstability followed the same pattern as volume, being very stable for anhour below 50° C. However, with the addition of shear from the extruder,we observed significant loss of volume and stability.

Denatured whey protein isolate looks quite different from thenon-denatured proteins at the ultrastructural level (FIG. 3). Assampled, denatured proteins (3A) (WPI extruded at 100° C.) are denselypacked with spacing of 2 to 6 nm, while non-denatured whey in the pasteare loosely packed with a large spacing 200 to 350 nm (3B). Thedifferences in fine structure of denatured and native whey protein areillustrated in FIGS. 3 and 4. In the “native” whey protein (40% slurry),the distribution of electron density surrounding the hydrating particlesin FIG. 1B is an open network with clear, electron-lucent spaces rangingfrom 15-40 nm and irregular structures of electron density of similardimensions. In contrast, the fine structure in segments where the wheyproteins are completely denatured is limited to close-packed finegranules around 3-8 nm in diameter (FIG. 3). The corresponding computedFourier transforms indicate that images of extrudate containing nativewhey proteins consist mainly of low spatial frequencies indicatingstructures with average spacings ranging from 15 to over 40 nm, whereasimages of extrudate containing denatured whey proteins have littleintensity at low spatial frequencies, but high intensity correspondingto high spatial frequencies, relating to electron density changesranging from about 3 nm to less than 10 nm (FIG. 4). The constraint ofextruding whey is keeping the temperature below the point where pyrosiswill occur as evidenced by relatively constant nitrogen content (Table2). We have seen evidence of fine structures with TEM images at 100° C.in whey isolates.

We have thus created structured networks in whey proteins using mildheat and shear, to create reversible denatured whey proteins. Byunderstanding on a molecular basis the effects of shear, ways ofcreating new functionality can be developed. This will enabledevelopment of extrusion parameters that permit controlled denaturationof whey proteins.

Extrusion processing denatured whey protein concentrates, wheylactalbumin (LAC) and whey protein isolate (WPI), but the greatestamount of denaturing occurred with WPI. Denatured whey protein isolateretained its native protein value, functionality, and digestibility whenextruded at 50° C. or below; changes in functionality occurred at 75 and100° C. Through careful selection of extrusion conditions, denaturedwhey proteins with unique functionality were produced. Denaturationincreased with temperature, but temperatures higher than 100° C. may beneeded to form denatured fibrous products from whey protein isolates. Weshow here that extrusion is an effective tool for denaturing wheyproteins to create denatured products.

Texturization is the process of inducing new form and function in apolymer (e.g., protein), for example using the extrusion shearingprocess described herein to change the globular non-fibrous conformationof proteins (e.g., whey protein isolates) into structured fibrous formsthat function differently. Extruding the whey protein isolate is whattexturizes it. Without extrusion, the conformation of whey proteinisolates can be changed (denatured) by heat or pH or pressure, but thereis no texturization. The texturization process described herein involvesheat, shear and pressure, unique conditions that denature and alsotexturize proteins such as whey protein isolates, with shear being themost important factor. Heat alone produces partially or totallydenatured milk proteins. Traditionally, milk proteins are denatured bymoist heat alone; this is the state of the art today and is accomplishedwithout shear and at temperatures below 75° C. for 30 to 90 minutes, sotexturization does not occur. Texturizing via the use of extrusion andheat accomplishes partial denaturation in less than 2 minutes in thetemperature range of 50° to 80° C.

All of the references cited herein are incorporated by reference intheir entirety. Also incorporated by reference in their entirety are thefollowing references: Aboagye, Y., and Stanley, D. W.,Can-Inst-Food-Sci-Technol-J., 20(3):148-153 (1987); Batterman-Azcona, S.J., and Hamaker, B. R., Cereal Chem., 75(2):217-221 (1998);Bhattarcharya, M., and Padmanabhan, M.,1999, Extrusion Processing:Texture and Rheology, In: “Wiley Encyclopedia of Food Science andTechnology (2nd Edition), Editor, Frederick J. Francis, John Wiley &Sons, New York, N.Y.; Farrell, H. M., Jr., et al., J. Dairy Sci.,85(3):459-471 (2002); Hale, A. B., et al., J. Food Sci., 67(3):1267-1270(2002); Harper, J. M., Extrusion of Foods, Vol. I., 1981, CRC Press,Boca Rotan, Fla.; Harwalkar, V. R., Michwissenchaft, 34(7):419-422(1979); Hong, Y., and L. K. Creamer, Int'l. Dairy J., 12:345-359 (2002);Kim, C. H., and J. A. Maga, Lebensmittel-Wissenchaft und-Technologie,20:311-318 (1987); Kester, J. J., and T. Richardson, J. Dairy Sci.,67(11):2757-2774 (1983); Kollengode, A. N., et al., J. Food Sci., 61(3):596-599, 603 (1996); Linden, G., and Lorient, D.,1999, Extraction andTexturisation Processes, In: New Ingredients in Food Processing, CRCPress, Boca Raton, Fla.; Martinez-Sema, M. D., and Villota, R., 1992,Reactivity, functionality, and extrusion performance of native andchemically modified whey proteins, pages 387-414 in Food ExtrusionScience and Technology, J. L. Kokini, C. Ho, and M. V. Karwe, ed.,Marcel Dekker, Inc. New York; Mohammed, Z. H., et al., J. Food Sci.,65(2):221-226 (2000); Kester, J. J., and T. Richardson, J. Dairy Sci.,67(11):2757-2774 (1983); Lin, S., et al., J. Food Sci., 67(3): 1066-1072(2000); Phillips, L. G., et al., J. Food Sci., 55(4):1116-1119 (1990);Singh, R. K., et al., J. Food Processing and Preservation, 15:285-302(1991); Taylor, S. M. and Fryer, P. J., Food Hydrocoll., 8 (1):45-61(1994); Walstra, P., T. J., et al., 1999, pages 189-199 in DairyTechnology: Principles of Milk Properties and Processes, P. Walstra, T.J. Geurts, A. Noomen, A. Jellema, and M. A. J. S. van Boekel, ed.,Marcel Dekker, Inc., New York; Yada, R. Y., et al., 1999, Proteins:Denaturation and Food Processing, In: “Wiley Encyclopedia of FoodScience and Technology (2nd Edition), Editor, Frederick J. Francis, JohnWiley & Sons, New York, N.Y.; U.S. Pat. No. 5,151,283.

Thus, in view of the above, the present invention concerns (in part) thefollowing:

A dietary composition produced by a process comprising (or consistingessentially of or consisting of) extruding a protein containing productthrough an extruder at about 50-about 450 rpm and at a temperature ofabout 40° to about 120° C. to produce said dietary composition, whereinsaid dietary composition contains partially denatured protein containingproduct or totally denatured protein containing product or mixturesthereof.

The above dietary composition, wherein the residence time of saidprotein containing product in said extruder is about 15-about 90seconds.

The above dietary composition, wherein said protein containing productis selected from the group consisting of milk, milk concentrate, milkprotein concentrate, whey, whey concentrate, whey protein isolate, wheyprotein concentrate, and mixtures thereof; or wherein said proteincontaining product is selected from the group consisting of wheyconcentrate, whey protein isolate, whey protein concentrate and mixturesthereof; or wherein said protein containing product is whey proteinconcentrate.

The above dietary composition, wherein said temperature is about 90° toabout 120° C., wherein said rpm is about 50-about 100 rpm, and whereinsaid dietary composition contains totally denatured protein containingproduct. A method of making a fiber enriched food product, comprising(or consisting essentially of or consisting of) adding the dietarycomposition (contains totally denatured protein containing product) toone or more food ingredients or adding one or more food ingredients tothe dietary composition (contains totally denatured protein containingproduct).

The above dietary composition, wherein said temperature is about 400 toabout 90° C., wherein said rpm is about 150-about 250 rpm, and whereinsaid dietary composition contains partially denatured protein containingproduct. A method of replacing starch in a food product, said methodcomprising (or consisting essentially of or consisting of) substitutingthe dietary composition (contains partially denatured protein containingproduct) for a portion of the starch. The above, said method comprising(or consisting essentially of or consisting of) substituting the dietarycomposition (contains partially denatured protein containing product)for >0-about 60% of the starch. The above method, wherein said foodproduct is a puffed or expanded food product. A food product prepared bythe above method. The above food product, wherein said food product is apuffed or expanded food product. The above food product, wherein saidfood product contains >0-about 80% of said dietary composition.

A food product comprising (or consisting essentially of or consistingof) at least one food ingredient and the above dietary composition.

The above food product, wherein said dietary composition containstotally denatured protein containing product and partially denaturedprotein containing product.

The above food product, wherein said dietary composition containstotally denatured protein containing product. A method of increasingfiber in the diet of a mammal, comprising (or consisting essentially ofor consisting of) feeding to said mammal the above food product whereinsaid dietary composition contains totally denatured protein containingproduct.

The above food product, wherein said dietary composition containspartially denatured protein containing product.

The above food product, wherein said food product is a puffed orexpanded food product and said dietary composition contains partiallydenatured milk protein containing product; the above food product,wherein said food ingredient is selected from the group consisting ofcorn, wheat, rice, barley, rye, potato, and mixtures thereof.

Other embodiments of the invention will be apparent to those skilled inthe art from a consideration of this specification or practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with the true scope and spiritof the invention being indicated by the following claims. TABLE 1Extrusion melt temperatures of whey proteins. Post-Extrusion ProductMelt Temperature (° C.) Pre-Extrusion (%) (%) WPC80 70 ± 2 40.9 59.9WLAC 75 ± 1 68.7 94.4 WPI 74 ± 1 28.0 94.8WPC80: Whey Protein Concentrate, 80% protein.WLAC: Whey Lactalbumin.WPI: Whey Protein Isolate: Number reported is mean of three samples.

TABLE 2 Properties of whey protein isolate (WPI) as function ofextrusion temperature. Insoluble Digestibility Extrusion Temp. (° C.)*pH Protein** (%) (%) (%) 35 6.7 90.7 28.4 89.6 50 6.8 90.9 33.3 88.2 756.9 91.7 77.7 85.7 100  7.0 91.4 87.2 84.5 PSD 0.2 0.7 1.2 0.6WPI: Whey protein isolates.*Preset barrel temperature of zones 6, 7, 8, 9.PSD: Pooled Standard Deviation.**% Protein after drying.Properties of non extruded WPI: pH 6.8, Protein 88.9%, Insoluble(Denatured) 28.0%, and Digestibility 87.7%.

TABLE 3 Physical properties of whey protein isolate (WPI) as function ofextrusion temperature. Extrusion Temp. Moisture Gel strength Foam volumeFoam (° C.)* (%) (N) (%) stability 35 42.5 114.9 298.1 29.8 50 40.9145.3 301.9 30.2 75 42.6 2.8 173.3 17.3 100  38.9 # 77.1 7.7 PSD 0.7 1.91.2 1.1WPI: Whey protein isolates.*Preset barrel temperature of zones 6, 7, 8, 9.PSD: Pooled Standard Deviation.Properties of non-extruded WPI: Moisture 1.94%, Gel Strength 52.3 (N),Foam volume 288%, and Foam stability 28.7%.#: Value Not Reported.

1. A dietary composition produced by a process comprising extruding aprotein containing product through an extruder at about 50-about 450 rpmand at a temperature of about 40° to about 120° C. to produce saiddietary composition, wherein said dietary composition contains partiallydenatured protein containing product or totally denatured proteincontaining product or mixtures thereof.
 2. The dietary compositionaccording to claim 1, wherein the residence time of said proteincontaining product in said extruder is about 15-about 90 seconds.
 3. Thedietary composition according to claim 1, wherein said proteincontaining product is selected from the group consisting of milk, milkconcentrate, milk protein concentrate, whey, whey concentrate, wheyprotein isolate, whey protein concentrate, and mixtures thereof.
 4. Thedietary composition according to claim 1, wherein said proteincontaining product is selected from the group consisting of wheyconcentrate, whey protein isolate, whey protein concentrate and mixturesthereof.
 5. The dietary composition according to claim 1, wherein saidprotein containing product is whey protein concentrate.
 6. The dietarycomposition according to claim 1, wherein said temperature is about 90°to about 120° C., wherein said rpm is about 50-about 100 rpm, andwherein said dietary composition contains totally denatured proteincontaining product.
 7. The dietary composition according to claim 1,wherein said temperature is about 40° to about 90° C., wherein said rpmis about 150-about 250 rpm, and wherein said dietary compositioncontains partially denatured protein containing product.
 8. A foodproduct comprising at least one food ingredient and the dietarycomposition according to claim
 1. 9. The food product according to claim8, wherein said dietary composition contains totally denatured proteincontaining product and partially denatured protein containing product.10. The food product according to claim 8, wherein said dietarycomposition contains totally denatured protein containing product. 11.The food product according to claim 8, wherein said dietary compositioncontains partially denatured protein containing product.
 12. The foodproduct according to claim 8, wherein said food product is a puffed orexpanded food product and said dietary composition contains partiallydenatured milk protein containing product.
 13. The food productaccording to claim 12, wherein said food ingredient is selected from thegroup consisting of corn, wheat, rice, barley, rye, potato, and mixturesthereof.
 14. A method of making a fiber enriched food product,comprising adding the dietary composition according to claim 6 to one ormore food ingredients or adding one or more food ingredients to thedietary composition according to claim
 6. 13. A method of increasingfiber in the diet of a mammal, comprising feeding to said mammal thefood product according to claim
 10. 14. A method of replacing starch ina food product, said method comprising substituting the dietarycomposition according to claim 7 for a portion of the starch.
 15. Themethod according to claim 14, said method comprising substituting thedietary composition according to claim 7 for >0-about 60% of the starch.16. The method according to claim 14, wherein said food product is apuffed or expanded food product.
 17. A food product prepared by themethod according to claim
 14. 18. The food product according to claim17, wherein said food product is a puffed or expanded food product. 19.The food product according to claim 17, wherein said food productcontains >0-about 80% of said dietary composition.